Chemokines are chemotactic cytokines, of molecular weight 6-15 kDa, that are released by a wide variety of cells to attract and activate, among other cell types, macrophages, T and B lymphocytes, eosinophils, basophils and neutrophils (reviewed in Luster, New Eng. J Med., 338, 436-445 (1998); Rollins, Blood, 90, 909-928 (1997); Lloyd, Curr. Opin. Pharmacol., 3, 443-448 (2003); Murray, Current Drug Targets., 7, 579-588 (2006); Smit, Eur J Pharmacol., 533,277-88 (2006)
There are two major classes of chemokines, CXC and CC, depending on whether the first two cysteines in the amino acid sequence are separated by a single amino acid (CXC) or are adjacent (CC). The CXC chemokines, such as interleukin-8 (IL-8), neutrophil-activating protein-2 (NAP2) and melanoma growth stimulatory activity protein (MGSA) are chemotactic primarily for neutrophils and T lymphocytes, whereas the CC chemokines, such as RANTES, MIP-1a, MIP-1, the monocyte chemotactic proteins (MCP-1, MCP-2, MCP-3, MCP-4, and MCP-5) and the eotaxins (-1, -2, and -3) are chemotactic for, among other cell types, macrophages, T lymphocytes, eosinophils, mast cells, dendritic cells, and basophils. Also in existence are the chemokines lymphotactin-1, lymphotactin-2 (both C chemokines), and fractalkine (a CXXXC chemokine) that do not fall into either of the major chemokine subfamilies.
The chemokines bind to specific cell-surface receptors belonging to the family of G-protein-coupled seventransmembrane-domain proteins (reviewed in Horuk, Trends Pharm. Sci., 15, 159-165 (1994); Murphy, Pharmacol Rev., 54 (2):227-229 (2002); Allen, Annu. Rev. Immunol., 25, 787-820 (2007)) which are termed “chemokine receptors.” On binding their cognate ligands, chemokine receptors transduce an intracellular signal through the associated trimeric G proteins, resulting in, among other responses, a rapid increase in intracellular calcium concentration, activation of G-proteins, changes in cell shape, increased expression of cellular adhesion molecules, degranulation, promotion of cell migration, survival and proliferation. There are at least eleven human chemokine receptors that bind or respond to CC chemokines with the following characteristic patterns: CCR-1 (or “CKR-1” or “CC-CKR-1”) [MIP-1a, MCP-3, MCP-4, RANTES] (Ben-Barruch, et al., Cell, 72, 415-425 (1993), Luster, New Eng. J. Med., 338, 436-445 (1998)); CCR-2A and CCR-2B (or “CKR-2A”/“CKR-2B” or “CC-CKR-2A”/“CC-CKR-2B”) [MCP-1, MCP2, MCP-3, MCP-4, MCP-5] (Charo et al., Proc. Natl. Acad. Sci. USA, 91, 2752-2756 (1994), Luster, New Eng. J. Med., 338, 436-445 (1998)); CCR3 (or “CKR-3” or “CC-CKR-3”) [eotaxin-1, eotaxin-2, RANTES, MCP-3, MCP-4] (Combadiere, et al., J. Biol. Chem., 270, 16491-16494 (1995), Luster, New Eng. J. Med., 338, 436-445 (1998)); CCR-4 (or “CKR-4” or “CC-CKR-4”) [TARC, MIP-1a, RANTES, MCP-1] (Power et al., J. Biol. Chem., 270, 19495-19500 (1995), Luster, New Eng. J. Med., 338, 436-445 (1998)); CCR-5 (or “CKR-5” OR“CCCKR-5”) [MIP-1a, RANTES, MIP-1p] (Sanson, et al., Biochemistry, 35, 3362-3367 (1996)); CCR-6 (or “CKR-6” or “CC-CKR-6”) [LARC] (Baba et al., J. Biol. Chem., 272, 14893-14898 (1997)); CCR-7 (or “CKR-7” or “CC-CKR-7”) [ELC] (Yoshie et al., J. Leukoc. Biol. 62, 634-644 (1997)); CCR-8 (or “CKR-8” or “CC-CKR-8”) [1-309, TARC, MIP-1p] (Napolitano et al., J. Immunol., 157, 2759-2763 (1996), Bernardini et al., Eur. J. Immunol., 28, 582-588 (1998)); CCR-10 (or “CKR-10” or “CC-CKR-10”) [MCP-1, MCP-3] (Bonini et al, DNA and Cell Biol., 16, 1249-1256 (1997)); and CCR31 (or “CKR-11” or “CC-CKR-11”) [MCP-1, MCP-2, MCP-4](Schweickart et al., J Biol Chem, 275 9550-9556 (2000)).
In addition to the mammalian chemokine receptors, the Decoy receptors CCX-CKR, D6 and DARC/Duffy as well proteins expressed by mammalian cytomegaloviruses, herpes viruses and poxviruses, exhibit binding properties of chemokine receptors (reviewed by Wells and Schwartz, Curr. Opin. Biotech., 8, 741-748 (1997); Comerford, Bioessays., 29(3):237-47 (2007)). Human CC chemokines, such as RANTES and MCP-3, can cause rapid mobilization of calcium via these virally encoded receptors. Receptor expression may be permissive for infection by allowing for the subversion of normal immune system surveillance and response to infection. Additionally, human chemokine receptors, such as CXCR-4, CCR2, CCR3, CCR5 and CCR8, can act as co receptors for the infection of mammalian cells by microbes as with, for example, the human immunodeficiency viruses (HIV).
Chemokine receptors have been implicated as being important mediators of inflammatory, infectious, and immunoregulatory disorders and diseases, including asthma and allergic diseases, as well as autoimmune pathologies such as rheumatoid arthritis, Grave's disease, chronic obstructive pulmonary disease, and atherosclerosis. For example, the chemokine receptor CCR3 is expressed among others on eosinophils, basophils, TH2 cells, alveolar macrophages, mast cells, epithelial cells, microglia cells, astrocytes and fibroblasts. CCR3 plays a pivotal role in attracting eosinophils to sites of allergic inflammation and in subsequently activating these cells. The chemokine ligands for CCR3 induce a rapid increase in intracellular calcium concentration, increased GTP exchange of G-proteins, increased ERK phosphorylation, enhanced receptor internalization, eosinophil shape change, increased expression of cellular adhesion molecules, cellular degranulation, and the promotion of migration. Accordingly, agents that inhibit chemokine receptors would be useful in such disorders and diseases. In addition, agents that inhibit chemokine receptors would also be useful in infectious diseases such as by blocking infection of CCR3 expressing cells by HIV or in preventing the manipulation of immune cellular responses by viruses such as cytomegaloviruses.
Therefore, CCR3 is an important target and antagonism of CCR3 is likely to be effective in the treatment of inflammatory, eosinophilic, immunoregulatory and infectious disorders and diseases (Wegmann, Am J Respir Cell Mol Biol., 36(1):61-67 (2007); Fryer J Clin Invest., 116(1):228-236 (2006); De Lucca, Curr Opin Drug Discov Devel., 9(4):516-524 (2006)
It has been found and disclosed in WO 2010 115836 that the substituted piperidines of formula 1 are highly suitable as CCR3 antagonists, having less side effects, e.g. inhibition of norepinephrine (NET), dopamine (DAT) or serotonin reuptake transporters (5-HTT) as described by Watson P S, Bioorg Med Chem Lett., 16(21):5695-5699 (2006), or inhibition of 5HT2A, 5HT2C or Dopamine D2 receptors as described by De Lucca, J Med Chem., 48(6):2194-2211(2005), or inhibition of the hERG channel as described by De Lucca, Curr Opin Drug Discov Devel., 9(4):516-524 (2006), or inhibition of the alpha1B adrenergic receptor.
Nevertheless the synthesis of these compounds was complicated, needed a lot of several steps and was very time consuming. Thus, the goal of the present invention is to provide a clean and fast way to synthesize compounds of formula 1 starting from commercially available educts.
Basis is a Lewis acid induced aminolyse which is also known from Mark W. Bundesmann et al. Tetrahedron Letters 51; 3879-3882; 2010. Nevertheless prior art does not cite that this reaction is also with optionally substituted pyridines like compound 2 (see below) possible.